Circuit breaker



.. Feb. 29,1944. A. w. KRIEGER 4 2,342,945

r v CIRCUIT BREAKER Filed Sept. '7, 19421 s sheets-'sheet 1 1:65529, 1944-V A. w. KRIEGER v CIRCUIT BREAKER Filed sept. '7, 1942 3 Sheets-Sheet 2 Feb. 29, 1944. A'. w KRIEGE 2,342,945

CIRCUIT lBREAKEIR i Filed sept'. '7, 19,42 3 sheets-shea s MEE-v l Patented.. 29,

CIRCUIT BREAKER Alvin Krieger, Milwaukee, Wis., assigner to Cutler-Hammer, Inc., Milwaukee, Wis., a corporation of Delaware Application September 7,1942, Serial No. 457,54?

(Cl. 20u- 116) 28 Claims.

This invention relates toA improvements in circuit` breakers, and although not limited thereto the invention relates particularly to overload circuit breakers for airplanesand the like.

A primary object of the invention is to mini- Cil mize the space requirements, and consequently the weight, -of such a device, While insm'ing trustworthyoperation thereof under all conditions.

Another object is to provide a manually controllable overload circuit breaker which is nontrip-free, to provide for attainment of an important and desirable result.

Another object is to provide a circuit-breaker of the aforementioned character which will withstand severe vibration Without accidental tripping thereof or arcing of its contacts.

Another object is to provide a circuit breaker which will perform in a normal manner under maximum night altitude conditions.

Another object is to provide acircuit breaker which is substantially unaffected. by variations in ambient temperature or pressure conditions. '4 Another object is to provide an overload circuit `breaker the various partsof which are much smaller and more compactly arranged than those of circuit breakers of similar capacity heretofore known.

Another and more specific object is to provide an overload circuit breaker whose frontal area is the same as that of `switches now standard for aircraft service.

Another object is to provide a manually controllable overload circuit breaker consisting of a group of elements most of which are common to such devices having a wide range .of different capacities.

Another object is to minimize the number of different parts required to afford the desired range of variation in the circuit controlling capacities of vsuch devices.

Another object is to provide a circuit breaker which may be manually closed and/or held closed regardless of overload conditions.

Another object is to provide a substantially dust-tight enclosure for the operating elements of such a circuit breaker.

Another, object is to provide novel means for indicating the circuit controlling condition ci the circuit breaker.

Another object is to provide novel means including a single manual lever for operating the switch mechanism and for simultaneously resetting the .overload mechanism after tripping of the latter.

Another object is to provide .fa novel form of.

combined switching and resetting lever, and a novel form of pivoting means therefor.

Another object is to facilitate' calibration land/or initial adjustment of such devices, and

to maintain such adjustment.

Various other objects and advantages ofithe invention `will hereinafter appear.

The accompanying drawings illustrate certain embodiments of the invention which willnow be described; it being understood that the embodiments illustrated are susceptible o f modification in respect of certain structural details thereof within the scope of the appended claims.

In the drawings,

Figure l is a top plan view, actual size, of a circuit breaker constructed in accordance with my invention.

Fig. 2 is a view thereof in side elevation.

Fig. 3 is an enlarged sectional view, on the line 3-3 of Fig. l, in the direction of the arrows.

Fig. 4 is a view quite similar to Fig. 3, but showing in elevation the elements other than the insulating bases-the various parts being shown in the respective positions assumed thereby after automatic tripping of the switch to open position as an incident to an overload of predetermined value--the form and manner of atbeing shown in' section.

Fig. e is a view, partly in side elevation and partly in vertical section (with certain elements shown in elevation) of a slightly modified form of device for control of a circuit employing a current of relatively low value, and.

Fig. 9 is a fragmentary View, inseetion on the line 9 9 of Fig. 8, showing the manner of supporting and affording adjustment of one end of the bimetallic member.

Referring first to that form of :my invention shown in Figs. i to 7, the numeral il) designates a base molded from any suitable insulating ma terial-preferably Bakelite." Base i0 is provided with a relatively deep but relatively short substantially rectangular recess iiifL which opens to the upper surface thereof, and with a relatively shallow but relatively long substantially rectangular recess ib which opens to the lower surface thereof; an approximately rectangular open- (not shown) extensions being respectively ing Illc being formed between said recesses to provide a communicating passage. The upper wall of recess lub is provided with a Agroove or channel lild (Fig. 3) to snugly receive, in a substantially flush relation, the horizontal portion IIa of a member il formed ofmetal strip material, one endof portion l la extending into alinement with opening Il)c and having a tip l2, of ne silver or other suitable contact material, spot welded, brazed, or otherwise rigidly and permanently attached thereto.

Said upper wall of recess Ib and portion Ila of member H are provided with alined openings to receive the shank of a headed' rivet i3, the end` of which shank is upset, as shown at I3, to rigidlysecure member Il in assembled position. The relatively lon-ger vertical portion llb of member ll is preferably spaced slightly from the inner surface of the end wall llle of recess l", said portion Hb extending downwardly to the point indicated in Fig. 3 for a purpose hereinafter described. 'Portion lib is provided at the point indicated with an inwardly pressed or extruded boss llc which is adapted to center one end of a coiled compression spring 3l which abuts against the innersurface of portion I Ib. Portion Ilb is provided near its lower end with a slot or substantially elliptical opening Hd, which is adapted to provide clearance forthe shank of a screw l5 which serves to clamp said end to another metal member I6, as hereinafter described.

As shown in Fig. 3, the upper end wall of recess lb is suitably recessed on the left-hand side of opening Il)c to snugly receive the at horizontal portion Il of a punched and stamped sheet metal member I1, said member having a relatively long vertical portion l'lb, which is notched on opposite side edges thereof adjacent to its lower end, as shown at I'lb and llc, the lower end portion 11d thereofbeing preferably bent inwardly at a right angle as shown (after final assembly of the` parts). 'Portion l'ld is provided with a tapped opening to receive, in an upward direction, the shank of a wiring terminal screw l8-a lock-washer I9 being preferably associated with the head of said screw, for a well known purpose.

The portion l'la of member l1 projects into alinement with opening |0 and the inner end thereof is notched or bifurcated, as indicated at Ile; said bifurcated end being bent upwardly at a right angle to provide a pair of spaced fulcrum arms or studs I'It and Hg (Figs. 3, 4 and 5). Said fulcrum studs are preferably located in a vertical plane at the mid-length of recess l0, and the same are adapted to form a pivotal supportl for a punched and stamped sheet metal contactor 20. Contactor 2li is preferably'provided with a relatively long, nat arm 211iL and a relatively short,` fiat arm h extending upwardly at an obtuse angle with respect thereto. The blank from which contactor 20 is formed :is provided on opposite sides thereof with integral extensions 2l!c and 20d (Figs. 3, 4 and 5); .Said

provided with outwardly pointed substantially triangular openings 2U@ and 201, so that upon bending said extensions upwardly into parallel planes at right angles to arms 20a and 20h (within the areas of said bearings) the slightly rounded points 2litz and 20h of said openings are adapted to act as downwardly `opening bearings which seat against the respective upper ends of the fulcrum arms l1* and l'l. As will b'e noted, the fulcrum point of contactor 20 (Figs. 3 and 4) is in a plane slightly to the (form,

right of the point of juncture of the aforementioned arms 20a and 20h. This insures tilting of the contactor in one direction or the other' as an incident to movement along arm 20a of the actuating element hereinafter described. Arm 2Gb actsas a rest for said element in the o pasition of the contactor, and insures against accidental movement of said element over the dead center.

As best illustrated in Fig. 5", arm 20a fits rather closely between the adjacent portions of arms IIf and Hg, whereby-lateral displacement of the contactor is prevented.` The rearwardly extending lugs 2l)h and 201 are adapted to seat against the bottom wall of recess HJ (Fig. 4) in the "olf" position of the contactor thus hunting the throw of the latter in that direction. Arm 2lia has welded or otherwise rigidly attached thereto a tip 2| corresponding to the tip l2 aforedescribed.

The operating means for contactor 20 comprises a metal lever 22 having a relatively long substantially cylindrical recess 22a opening to the lower end thereof. A coiled compression spring 23 is positioned within said recess, and a substantially cylindrical plunger 24, of any suitable insulating material, such as Bakelite is adapted to seat against said spring; plunger 24 preferably having a reduced upper end 24a adapted to telescope into one or more of the lower end coils of the spring, and the lower end 24h of said plunger being of rounded or convex form to facilitate movement thereof relatively to the contactor. Spring 23 at all times acts to bias plunger 24 outwardly from recess 22a, to provide a predetermined minimum degree of pressure of the plunger against the contactor.

Lever 22 is provided exteriorly thereof, at a point intermediate the length of recess 22a, with a downwardly facing annular shoulder 22". A metal ring 25 is adapted to t closely onto lever 22, said ring having a flat upper edge 25a adapted to seat against shoulder 22b and a i'lat lower edge 25h. A punched and stamped sheet metal member 26 of substantially inverted U- shape in vertical cross section has its perforated flat connecting portion 2lia tted onto lever 22, as shown, and seatedagainst the lower edge 25b of said ring. An integral annular portion of lever 22 is upset over the inner surface of connecting portion 25, as shown at 22c (Fig. 3) to rigidly and non-rotatably secure ring 25 and member 26 to lever 2 2, and to each other.

AS shownin Figs. 4 and 5, ring 25 is provided with a pair of diametrically opposite integral lateral projections 25c and 25d of cylindrical said projections serving jointly as a pin for lever 22. As shown in Figs. 2 and 5, the opposite side walls lfand Illg of recess HlSL are lprovided at the mid-length of the upper edges thereof with upwardly opening notches Il)h and lifthe bottom walls of which are preferably of arcuate form (see Fig. 2) to provide bearings for the respective projections 25 and 25d of ring 25. The depth of notches Illh and Ill-is preferably slightly greater; than the diameter of projections 25 and 25d to afford free rotation of the latter after attachment of the combined supportingand cover plate 2'.' formed of sheet metal, which serves to retain sat'd projections within saidl bearing notches. Plate 21 is provided with a circular opening 2 which aords oscillating clearance for lever 22. Fig. 3, opening 21a and ring 25 are so As best illustrated in is of such a size, and lever22 formed, as to provide for sub pivot amano stantial closure of said opening in all positions of the lever.

Base I preferably has molded into its upper surface four metallic inserts, the hollow upwardly extending shanks of which are accommodated by a corresponding number of openings in said combined supporting and cover plate 21, said shanks being upset over said plate as shown at 28 in Figs. 1 to 4 to secure said parts in assembled relation.

The parallel downwardly extending arms 26h and 2lic of member 26 are of substantially inverted triangular form, and the opposite angular edges of the same jointly are adapted to engage pairs of integral vertical abutment surfaces formed by, or as continuations of, the Walls of opening Hic-certain of said abutments being shown at lul, ilk and 01 in Figs. 3 and 4-to positively limit the throw of lever 22 in'each direction. As shown in Figs. 3, 4 and 5, arms 2Gb and 26c extend downwardly through opening Il)c into recess Ill",I and the right-hand edges of said arms are adapted for cooperative engagement with alined vertical shoulders formed upon opposite sides of a member 29, molded from a suitable insulating material, such as Bakelite"; one of said shoulders being shown at 29a in Fig. d, and the width of each being indicated by the dotted lines vat 29a and 29b in Fig. 5. Said shoulders (see 29a.) are formed between a relatively wide right-hand portion 2l!c whose opposite fiat sides (one of which is shown at 29d in Fig. 4) are freely slidable between the side walls of recess lub, and a relatively narrower left-hand portion 29e whose opposite at sides (one of which is shown at 29f in said ligure) are freely slidable between the vertical Walls of integral portions of base l0, one of said walls being shown at Hlm in Fig. 3.

Member 29 is provided with upper and lower fiatsurfaces 29g and 29h (Figs. 3 and 4); the

surface 29g being adapted to slidably engage the downwardly facing flat surfaces of a pair of spaced integral ledge portions formed upon the upper end wall of recess illb, one of said surfaces being shown at |011 in Figs. 3 and 4. The lower surface 29h of member 29 is adapted to be positioned in a substantially flush relationship to the lower end of base l0 for sliding engagement thereof with a flat punched insulating plate 30, preferably formed of canvas- (or other fabric) reinforced Bakelite Member 29 is provided with a substantially cylindrical recess 281 (Fig. 3) which is adapted to accommodate a relatively strong coiled compres-f sion spring 3l, the outer-end of which is adapted to surround the aforementioned boss I l and engage the portion l Ib of member l I, whereby spring 3l normally biases member 29 toward the member 3S. Plate 32 is provided with an up.

wardly extending substantially hemispherical boss 32Br which fits into the lower Aend of a coiled compression spring 34 positioned within recess 29k, Member 33 is provided at the left-hand end thereof (Fig. 3) with a relatively narrow lug 33a which is adapted to be positioned within recess 295, lug 33e being bent upwardly at substantially 5 a right angle to the main b'ody of member 33.

Member 33 is provided at its right-hand end with a relatively narrow lug 33h which is bent to extend upwardly and inwardly at an acute angle to said main body portion, said angle Acorresponding to the angle of the end wall 29 of recess 29. Member 33 has sheared from the main body thereof and bent downwardly therefrom at an acute angle a latching lug 33. Plate 32 is notched at its opposite ends to accommodate the root portions of lugs 33.a and 33h, whereby plate 32 and member 33 are restrained against lateral displacement with respect to each other.

Spring 34 thus acts to bias the main body portion of member 33 against the aforementioned plate 30 while biasing member 29 in an upward direction. Plate is provided with a relatively long slot 30a (Fig. 3) to provide slidable clearance for lug 33, which extends downwardly a predetermined distance therebel'ow.

Member 29 is provided at its left-hand end .(Fig. 3) with an upwardly opening groove 29D having an angularly extending bottom wall 29q which acts as a cam surface for cooperation with the rounded lower end 35a of plunger 35, which 3o is preferably composed of metal and machined to the form thereof best illustrated in Fig. 3. Thus the cylindrical lower end portion 35h of said plunger is slidable within a passage it* formed in the wall between recesses H18 and i 3b. Plunger 35 35 is provided with an annular ilange 35 the lower surface of which acts to limit downward displacement of the plunger, and the upper surface of which acts as an abutment for the lower end of anoiled compression spring 36 which surrounds the plunger, the upper end of said spring being adapted to abut the inner surface of plate 21 to bias the plunger to the extreme lower position thereof shown in Fig. 3.

Plate 21 and a panel 3l (to which the circuit breaker is attached, as by means of a pair of screws or bolts 38, 39) are provided with aimed openings to accommodate the reduced cylindrical upper end portion 35d of said plunger; the upper end surface 35 of portion 35d being preferably provided with a coating of paint or enamel (such as black, to correspond with the color of the outer surface of panel 3'!) to render the same invisible or inconspicuous in the normally retracted position of the plunger, and the upper end part of portion 35d being preferably provided with a coating of paint or enamel of a highly contrasting color (such as red) to render the same conspicuous when projected in the manner illustrated in Fig. 4. Portion 35d when thus projected serves to indicate that the switch mechanism has been tripped to circuit-interrupting position as an incident to the occurrence of an overload of predetermined value and/or of predetermined duration within the controlled circuit. The manner 'in which the cam surface 29q acts against the lower end of plunger 35 to project the latter is believed to be apparent from Figs. .3 and 4.

As shown in the various gures (see Fig. l) plate 21 is provided with embossed upwardly projecting, interrupted rib portions along opposite sides thereof, as indicated at 2lb, to seal against the inner surface of panel 3l', thus providing clearance between said inner surface and the upset ends of Shanks 28 aforementioned,

ber portions having untapped openings (not-l, shown) therein the walls of which grip the' Shanks of bolts 38 when threaded into the metal portions of said nuts.

The means for latching member `29 in its re-1 tracted position against the bias of spring 3| (as shown in Fig. 3) comprises a bimetallic strip 4| of predetermined caliber which is supported within a recess 42 which opens to the upper end of the lower insulating ,base 42, which likewise preferably'consists of molded Bakelite." One end 4| (of reduced width) of strip 4l is adapted to seat against the upwardly facing edge or wall of an opening I6a (Fig. 3) formed in the aforementioned punched and stamped sheet metal member I6, the vertical portion of which is provided witha-tapped opening Il;b to accommodate the shank of-screw'l5 whereby members and I6 are mechanically and electrically connected to each other. The portion l6 of member I6 is bent toward the left (Fig. 3) at substantially a right ang-le to the vertical portion thereof, and portion 16 is provided with a pairlof integral arms I6d and Iiie (Fig. 6) extending at a predetermined angle relatively to each other, said arms having openings formed therein to accommodate the hollow Shanks of a pair of headed ings alined with openings formed in the bottom wall of recess 42 to accommodate the hollow shanks of headed rivets 49, 49, which Shanks are upset as shown at 49 to rigidly secure said members to'base 42. Said bottom wall of recess 42 is provided with an opening 42b through which the relatively short arm extends in a downward direction, and with an opening 42 to accommodate the relatively long arm 43b when in a straight condition. After securement of members 46 and 48 to base 42 the lower end portion 48 of arm 48b is preferably bent at a predetermined angle toward the right (as shown in Figs. 3 and 4),

said portion 48. being provided with a tapped opening to accommodate the shank of a wiring terminal screw I8 like that associated with the aforementioned member l1.

Strip 4I has attached to the relatively wide intermediate portion 4| thereof (Figs. 4 and 6), as

by spot-welding, the horizontal portion of a metal member, which is preferably formed of steel. Member 50 has a latch portion 56 bent upwardly at Substantially a right angle thereto, the upper edge of portion 56 being beveled upwardly toward the right (Figs. 3 and 4) to serve as a cam to permit passage of portion 33 of member 33 thereover when member 29 is moved toward 'its right-hand extreme position from the position thereof shown in Fig. 4, to effect cci-operative engagement of the latching lugs 33 and 50 upon manual release of lever 22 when the strip 4| is in its normal or relatively cool condition.

rivets 43 (see Fig. 7) which extend upwardly through openings provided in the bottom wall of recess 421. Also as best illustrated in Fig. 6, a member 44 of highly resilient metal such as phosphor bronze, is superimposed upon the portion |6 of member I6, said member 44 having integral arms 44 and 44b the ends of which are likewise perforated to accommodate the Shanks of rivets 43, said Shanks being upset as shown at 43a in Fig. 6 to secure members I6 and 44 to base 42. Member 44 is provided with an integral lug 44 bent downwardly at substantially a right angle thereto, said lug 44 being adapted to penetrate opening I6EL in member I6 and engage with a predetermined degree of pressure the upper surface of end portion 4| of said strip to hold the latter against said upwardly facing edge of opening IBB.

In practice a short length of multiple-strand) wire 45, of copper or the like, has its respective ends spot-welded or otherwise'rigidly attached to member i6 and to strip 4| to insure a, good electrical connection therebetween. The other end 4|b (of reduced width) `of strip 4| is adapted to extend toward the left (Fig. 3) through an opening 46 formed in a metal member 46, one end portion 46b of member 46 being bent upwardly at substantially a right angle to the main body. portion thereof, and the upper edge or end wall 46 of said opening being adapted to overlie said portion 4lb of the bimetalli'c strip. A suitable' length of multiple-strand copper wire 4'! is spotwelded to strip 4I and to member 45 to insure a good electrical connection therebetween. The right-hand portion of member 46 (Figs. 3 and 4) overlies a metal member 48 of substantially inverted U-Shape; members 46 and 48 having'open- As shown in Fig. 3 there is preferably a predetermined normal degree of overlap between the lugs 33 and 56 when in latched relation, so that a suicientsdegree of downward movement of lug 56 to eiect disengagement thereof vfrom lug 33 will occur within apredetermined period after the occurrence ofthe degree of overload in the circuit to which thelbreaker is adapted to respond. However, in practice it is desirable to provide for initially adjusting the device in a manner to preselect any one of a number of diierent time periods of response thereof to a given overload condition in the controlled circuit. Said means as shown preferably comprises a screw 5I adapted for cooperative threaded engagement with a threaded passage 42d in the bottom wall of recess 42. Screw 5| has a reduced upper end portion 5| the rounded upper end Sib of which underlies the end portion 4|b of Strip 4| directly beneath the edge 46 of the opening in member 46. As'will be understood, member 46 is resilient, andthe arrangement isesuch that prior to assembling of vscrew 5|, as shown in Fig. 3, the left-'hand end of member 46 will .be bowed or bent downwardly to some extent from the position thereof illustrated. It follows that the end portion Sib of the screw when driven to the point illustrated has caused a predetermined degree of upward bendingof member 46, with a consequent clamping of end 4|b of the strip between the screw end 5I and Said edge 46. x

If it is desired to initially provide for an increased time period of response of the device to the predetermined overload condition, it is only necessary to drive the screw '5| upwardly to a greater extent within the threaded passage 42d, with consequent upward displacement of the lefthand end 4Ib of the bimetallic-strip 4|. This, of course, effects an upward displacement of lug 56 relatively to lug 33, so that a longer time period will be required to eiect disengagement of lug 50 from lug 33 under given overload conditions.

Conversely, vii' it is desired to initially provide for a shortervperiod of response of the device to a given overload condition, it is only necessary to unthread the screw to the desired extent with respect to passage 42*i whereby the lug 50B is lowered with respect to lug 33, with a consequent -reduction in the time required for the strip 4| to effect disengagement of lug 50' from lug 33 under said overload condition.

After the desired adjustment of screw has been effected, I prefer to partially ll the countersink or recess 42t in which the kerfed end 5lc thereof -is located with a quantity oi.' material 53,

.such as a porcelain type cementto insure against accidental loosening of the screw-whereby the initial or factory adjustment of the device is maintained.

As shown in Figs. 3 and 4, an opening 4i.'e is provided in the bottom wall of recess 4t2n to enable'downward passage oi' the lower end portions of members II and I6 therethrough prior to assembly of screw I5.

From the foregoing description it will be apparent that, with the parts of the device in the relative positions thereof shown in Fig. 4 (wherein the strip 4| has responded to the predetermined overload condition to effect tripping of 'the switch to circuit interrupting position), the switch may nevertheless be immediately reclosed by manualoperation of lever 22 to its left-hand extreme position shown in Fig. 1, and said switch may be maintained closed by manual retention of lever 22 in said extreme left-hand position notwithstanding-continuance of such overload condition in `the circuit.

This feature is of great practical importance and utility in respect of the use for which the device is intended, inasmuch as it provides for maintenance of a given device (such as a gun upon an airplane) in operation as long as possible; even though the operating motor is eventually burned out.

With the parts in the positions thereof shown in Fig. 4, but with the bimetallic strip 4| cooled sufliciently to permit return of lug 50 to a position wherein it will act toglatch lug 33, it is obvious that upon movement of lever 22 to `its lefthand extreme position theV switch will not only be closed, but upon coincident movement of member -23 to its extrme right-hand position (Fig. 3) lug 33 will cam or ride over lug 50, and upon manual release of lever 22 lug 5l)a will coact with lug 33c to hold member 29 against the bias of spring 3|, so that the switch will remain closed. With member 29 so restrained by lug 50 against the bias of spring 3|, it is also obvious that the switch may be manually operated at will to open or closed position without in anywise affecting the latching connection between lugs 50a and 33C. However, upon the occurrence of the predetermin d overload condition, lug 50a will be retracted ownwardly by strip 4| to effect release of member 28 which will be moved by spring 3,| to the left-hand position shown in Fig. 4, thus automatically effecting opening'of the switch.

The devices hereinabove described are adapted for control of circuits having ratings of from 6 amperes to 50 amperes. For this purpose the bimetallic strip 4| may have any one of a number of different calibers to correspond to certain of the ampere ratings aforementioned. Forother of the various ampere ratings either one or two shunting straps of the character shown in dotted lines at `52 in Figs. 4 and 7 may be employed. Said straps are preferably in theA form of suitable lengths of resistance ribbon composed of "Ad- Vance metal, which is obtainable commercially;

the bent 'ends of each of said straps being spotwelded, brazed or otherwise rigidly and permanently attached to the member I and to the arm 48s of member 48, said straps being bent or bowed outwardly at 52 to afford ample electrical clearance between the same and arm 48b of member 48 (see Fig. 7).

Base l0 is preferably provided with ledges Il)s and ||it offset downwardly from the upper surface thereof (Fig. 2), and base 42 is also preferably provided withledges offset upwardly from the lower surface thereof, two of said ledges being shown at 42h in Fig. 2; said bases having alined passages at each of the four corners thereof communicating with saidledges, for the reception of headed rivets 54 the hollow shank ends of 4which As will be apparent from the drawings, the

various parts within the several recesses In, Il)b and 42a are well protected against the entry of dust or other foreign matter.

The modified form of device illustrated in Figs.

8 and 9 is in most respects identical with that aforedescribed, and parts thereof corresponding to those in Figs. 1 to '7 having been designated by like numerals of reference. Thus, while I have shown the base I0 in side elevation, it is to be understood that the various parts associated therewith are identical with the corresponding parts aforedescribed. In Figs. 8 and 9, however,

`the metal member 46 and the multiple strand 4wire 41 are omitted, and a bimetallic strip 55 is r substituted for the strip 4| aforedescribed. Strip 55 has spot-welded or otherwise rigidly attached to the lower surface of the left-hand end portion 55b thereof one end 56' of a relatively still strip or ribbon of a suitable resistance metal, such as the nickel-chromium alloy sold commercially under the trade name of Nichrome The main body portion 56 of said strip is offset downwardly .to a slight extent to lie in a plane parallel to the bimetallic strip 55, to act as a heater for the latter. Strip 56 has a portion 56b bent downwardly at substantially a right angle to said main body portion thereof to lie against the arm 481 of member 48 and the end portion 48 of said arm, as shown at 56. Portions 56c and 56" are preferably spot-Welded or otherwise rigidly mechanically and electrically connected at one or more points to end 48c and arm portion 48h, re-

spectively, of member 48; said portion 56c being provided with an opening (not shown) to afford clearance for the shank of screw |8.

The left-hand end portions 55b and 56a of the strips 55 and 56 are preferably provided jointly with an outwardly opening notch 55", 56", which is adapted to accommodate the reduced portion or neck 51a ofan adjusting screw 51, screw 51 having an enlarged portion or flange 51b at the upper end thereof which'overlies a portion of the end 55b of strip 55 to limit upward movement of said end. A coiled compression spring 58 surrounding screw 51 is interposed between end 56 of the heater strip 56 and the bottom wall of recess 62a to bias the left-hand end of strip 55h against flange 51h. Screw 51 may be initially adjusted within passage 52d in the same manner as the aforedescribed screw l to predetermine the time period of response of the device to a given overload condition in the controlled circuit. A device like that disclosed in Fig. 8 is adapted for use in a low current carrying circuit, say, five amperes. The heater element 56 has theA effect of modifying the operating characteristics of the strip 55 under given overload conditions, as will be readily understood by those skilled in the art.

I claim:

1. In an electro-thermally responsive overload circuit breaker, in combination, a switch biased to open position and adapted for manual movement to and retention in closed position at will, a normally flat bimetallic strip of predetermined length and caliber, means for connecting said strip in the circuit controlled by said switch to provide for influence of the former by the current condition in said circuit, a latch member rigidly attached to said strip intermediate 4the ends of the latter and projecting therefrom at substantially a right angle thereto to normally retain said switch in closed position when manually closed, means for xedly supporting said strip at each end whereby the same is adapted to bow between its ends to effect retraction of said latch member under given conditions, the supporting means for one end of said strip comprising a stationarily supported screw manually in a predetermined plane, said means at one end of the strip comprising a stationary'screw manuallyadjustable to vary the normal plane o'f said strip and of said latch, to thereby require more or less bowing of said strip between the ends thereof for release of said switch, and said switch being adapted for movement to and retention in closed positional; will independently of said latch member.

4. In an electro-thermally responsive overload circuit breaker, in combination, a manually operable switch mechanism normally biased to circuit interrupting position, a bimetallic strip of predetermined caliber included in the circuit controlled by said switch, a latch member carried by said strip and cooperating with said switch to normally'hold the latter, when closed, in circuit completing position against said bias, normally fixed means at each end/.of said strip for supporting the same in a predetermined plane and in a manner to prevent substantial enclwise movement thereof in either direction, said means at one end of the strip comprising a resilient adjustable to move said end of the. strip to vary v the normal plane of the latter whereby the normal position of said latch member is correspondingly varied to subject said latch member to adjustment of its critical range of movement by saidmetallic strip.

2. In an electro-thermally responsive overload circuit breaker, in combination, a bimetallic strip of predetermined caliber, means for connecting said strip in an electric circuit to provide Y for response thereof to a given overload condition in the circuit, alatch member attached to said strip intermediate the ends of the latter, means for supporting said strip at each end in a manner to insure against substantial endwise movement thereof in either direction, the supporting means for one end of said strip comprising a resilient metal member and a separately supported screw between which said end is interl posed, said screw being manually adjustable to move said metal member and said end of'the strip to vary the normal plane of the latter, whereby the initial position of said latch member is correspondingly varied to thereby predetermine the period of latch-tripping response of said bimetallicstrip to a given overload condition, and means including one or more conducting metal straps included in the circuit in shunting relationship to said bimetallic stripfto thereby vary the value of the overload condition in said circuit to which said bimetallic strip is y adapted to respond to trip said latch.

3. In an electro-thermally responsive overload circuit breaker, incombination, a manually operable switchmechanism biased to circuit interrupting position, a'normally flat bimetallic strip of predetermined caliber included in the circuit controlled by said switch, a projecting latch member carried by said strip and cooperating with said switch/when closed to normally hold the latter against said at each end of said strip for supporting the same bias, normally lfixed means metal member and a manually adjustable screw, said screw when manually adjusted being adapted to vary the initial plane of said strip and the corresponding initial position rof said latch, to thereby vary the time element of response of said bimetallic strip for tripping of said switch under a given overload condition, and means comprising one or more conducting straps included in the circuit in shunting relationship to said bimetallic strip, to thereby vary the value of the overload condition in said circuit to which -said bimetallic strip is adapted to respond to trip said latch.

5. In an electro-thermally responsive overload circuit breaker, in combination, a manual lever operated switch mechanism normally movable to and resiliently retained in either its circuit completing or circuit interrupting position according to the direction of movement of said lever, overpowering spring operated means associated with said switch mechanism and normally tending to bias the same to circuit interrupting position, a normally ilat bimetallic strip of predetermined caliber included in the circuitcontrolled by said switch, a projecting latch member 'carried by said strip and cooperating with said spring operated means to normally render the latter ineffective to open the switch -upon movement thereof to closed position, normally fixed means at each end of said strip for supporting the same in a predetermined plane' and ina manner to r/ independently of said latch member.

6. In an electro-thermally responsive overload circuit breaker, in combination, a manual lever operated switch mechanism normally movable to and resiliently retained in either its circuit completing `or circuit interrupting position according to the direction of movement of said lever, overpowering spring operated means associated with said switch mechanism and normally tending to biasthe same to circuit interrupting position, a normally flat bimetallc strip of predetermined caliber included in the circuit centrolled by said switch, a projecting latch member carried by said strip and cooperating with said spring operated means to normally render the latter ineffective tov open the switch upon movement thereof to closed position, normally iixed means at each end of said strip for supporting the same in a predetermined plane vand in a manner to prevent substantial endwise movement thereof in either direction, said means at one end of said strip comprising a resilient metal member and a manually adjustable member, said last mentioned member when manually adjusted being adapted to vary the initial plane of saidstrip and the corresponding initial, position of said latch, to thereby vary the time element of response of said bimetallic strip for release of said spring operated means with consequent opening oi said switch under a predetermined overload condition, and said lever being manually operable to effect and maintain completion of the controlled circuit regardless -of said predetermined overload condition in the latter.

7. In an electro-thermally responsive overload circuit breaker, in combination, a manual lever operated switch mechanism normally movable to and resilientlyretained in either its circuit completing or circuit interrupting position according to the direction of movement of said lever, overpowering spring operated means associated with said switch mechanism and normally tending to bias the same to circuit interrupting position, a bmetallic strip of predetermined caliber included in the circuit controlled by said switch, a latch member carried by said strip and cooperating with said spring operated means to normally render the latter ineiective to open the switch upon movement thereof to closed switch upon movement thereof to closed position, normally iixed means at each end of said strip for supporting the same in a predetermined plane and in a manner to prevent substantial endwise movement thereof in either direction, said means atv one end of said strip comprising av resilient metal member and a manually adjustable clamping screw, said screw when manually adjusted being adapted to vary the initial plane of said strip and the corresponding initial position of said latch, to thereby vary the time element of response of said bimetallic strip for release of said spring operated means with consequent opening of said switch under a predetermined overload condition, and means comprising a spring-retracted indicating element associated with said spring operated means and projected by the latter upon release thereof by action of said bimetallic strip, to thereby indicate attainment of said predetermined overload condition in the controlled circuit.

9. In an electro-thermally responsive overload circuit breaker, in combination, a manual lever operated switch mechanism normally movable to and resiliently retained in either its circuit completing or circuitfinterrupting position' according to the direction of movement of said Y lever, overpowering spring operated means assoposition, vnormally fixed means at each end of said strip for supporting the same in a predetermined plane and in a mannerto prevent substantial endwise movement thereof in either direction, said means at one end of sa'id strip'comprising a resilient metal member and a manually adjustable screw, said screw when manually adjusted being adapted tov vary the initial plane of said strip and the corresponding initial position of said latch, to thereby vary the time element of response of said bimetallic strip for release of said spring operated means wth consequent opening o1' said switch under a predetermined overload condition, and means comprising at least one conducting metal strap arranged in` shunt relationship to said bimetallic strip, to thereby vary the value oi overload condition in said circuit to which said bimetallic strip is adapted to operatively respond.

8. In an" electro-thermally responsive overload circuit breaker, in combination, a manual lever operated switch mechanism normally movable to and resiliently retained in either its circuit completing or circuit interruptingposition accordingto the direction of movement of said lever. overpowering spring operated means assiciatedwith said switch mechanism and normally tending to bias the same to circuit interrupting posi- ,tion, a bimetallic strip of predetermined caliber included in the circuit controlled by said switch, a latch member carried by said strip and`cooperating with-said spring operatedm ns tonermally render the latter inei'fectiv'e"'vv open the ciated with said switch mechanism and normally tending to bias the same to circuit interrupting position, a bimetallic strip of predetermined caliber included in the circuit controlled by said switch, a latch member carried by said strip and cooperating with said spring operated means to normally render the latter ineffective to open the switch upon movement thereof to closed position, normally fixed means at each end of said strip for supporting the same in a predetermined plane and in a manner to prevent substantial endwise movement thereof in either direction/,said means at one end of said strip comprising avreslient metal member and a manually adjustable clamping screw, said screw when manually adjusted being adapted to vary the initial plane of said strip and the corresponding initial position of said latch, to thereby vary the time element of response of said bimetallic strip for release of said spring operated means with consequentopening of said switch under a predetermined'overload condition, means comprising a spring-retracted indicating element associated with said spring operated means and projected by the latter upon release thereof by action of said bimetallic strip, to thereby indicate attainment of said predetermined overload condition in the controlled circuit, said ind-'cating element having an exposed end surface which is substantially invisible in its environment when retracted, and the same having l.an adjacentportion of highly contrastingvcolor adapted to be exposed as an' incident to projection thereof.

10. In a circuit breaker, in combination, a molded insulating base having recesses respectively, opening to the upperA and lower surfaces thereof with a communicating opening therebetween, a pair of sheet metal members rigidly secured iiatwise to the upper end wall of the lower recess. each of said membe/rs having a portion thereof projecting into said opening, one of said portions being adapted to provide a stationary contact. the other portion being bifurcated and bent upwardly to prjovide a pair of spaced fulcrum arms located within the 'upper recess, a punched and stamped sheet metal contacter having arelatively long arm and a` relatively short ann arranged at an obtuse angle with respect to each other, said long arm being adapted for movement into or out of engagement with said contact, said contactor having Ioutwardly pointed substantially triangular openings formed in opposite sides thereof, said sides being bent upwardly into substantially parallel relation within the respective areas of said openings to provide bearings for engagement with said fulcrum arms, said upper recess having a pair of alined upwardly opening bearing notches formed in the side walls thereof, a lever having lateral pivot extensions positioned within said notches in a substantially ush relationship to the upper sur- .face of said base, a metal plate overlying the upper surface of said base and rigidly attached thereto to retain said pivot extensions within said bearings, said plate having an opening to provide oscillating clearance for said lever, and

'an insulating plunger spring biased outwardly from the recessed lower end of said lever to effect tilting movement of said contactor into or out of engagement with said contact upon movement of said lever in opposite directions respectively.

11. In a circuit breaker, in combination, a molded insulating base having recesses respectively opening to the upper and lower surfaces thereof with a communicating opening therebetween, a pair of sheet metal members rigidly secured flatwise to the upper end wall of the lower recess, each of said members having a portion thereof projecting intg said opening, one of said portions being adaptd to provide a stationary contact,'the other portion being bifurcated and bent upwardly to providea, pair of spaced fulcrum arms located within the upper recess, a punched and stamped sheet metal contactor having a relatively long arm and a relatively short arm arranged at-an obtuse upward angle with respect to each other, said long-arxn being adapted for movement into or out of engagement with -said contact, said contactor having outwardly pointed substantially triangular openings formed in opposite sides thereof, said sides being bent upwardly into substantially parallel -relation within the respective areas of said openings to provide bearings for engagement with said fulcrum arms, said upper recess having a pair of alined upwardly opening bearing notches formed in the side r walls thereof, a lever having lateral pivot extensions positioned within saidnotches ina substantially flush relationship to the upper surface ofV said base, a'metal plate overlyingthe upper surface'of said baseand rigidly attached thereto to retain said pivot extensions within said bearings, said plate having an opening to provide oscillating clearance for said lever, an insulating plunger spring 'biased outwardly from the recessed lower end of said lever to effect tilting movement of saidvcontactor into or out of engagement with said contact upon movement of said lever in opposite directions respectively, one of said first mentioned sheet metal members having a wiring terminal element formed integrally end is normally engaged under pressure with said spring whereby the lower end of said plunger is biased outwardly from said recess, said lever having an exterior, downwardly facing, annular shoulder formed thereon intermediate the length of said recess, a metal ring the upper edge of which is adapted to seat against said shoulder, an integral annular portion upon the exterior of said lever being upset to underlie the lower edge of said ring whereby the latter is retained in lassembled position, and said ring having diametrically opposite integral lateral extensions of substantially cylindrical form adapted for pivotal engagement with bearings formed in a suitable support, whereby said lever is limited to oscillatory movement in a single plane. a

13. A metal switch lever having a relatively long substantially cylindrical recess opening to the lower end thereof, a coiled compression spring positioned within said recess, a substantially cylindrical insulating plunger Whose upper end is vnormally engaged under pressure with saidspring whereby lthe lower end of said plunger is biased outwardly from said recess, said lever having an exterior, downwardly facing, annular shoulder formed thereon intermediate the length of said recess, a, metal ring the upper edge 'of which is adapted to seat'against said shoulder, a punched and stamped sheet metal member of substantially inverted U-shape, the connecting portion of said U being perforated to accommodate said lever whereby the outer surface of the former is adapted to seat against the lower edge of said ring, an integral annular portion upon the exterior of said lever being upset to underlie the lower surface of said connecting portion of the U whereby the latter and said ringmare retained in assembled relation to said lever, and said ring having diametrically opposite integral lateral extensions adapted for pivotal engagement with a suitable support.

14. A-metal switch levery having a relatively long substantially cylindrical recessv opening to end is normally'engaged under pressure with y said spring whereby the lower end of said plunger is biased outwardly'from said recess, said lever therewith, and the other of said members being having an exterior, downwardly facing, annular shoulder formed thereon intermediate the length of said recess, a metal ring the upper edge` of which is adapted to seat against said shoulder, a-punched and stamped sheet metalmember of substantially inverted U-shape, the connecting portion of said U being perforated to accommodate said lever 'whereby the outer surface of the former is adapted to seat against the lower edge of said ring, an integral annular portion upon vthe exterior of said lever being upset to underlie the lower surface of said connecting portion of the U whereby the latter and said ring are re'- tainedin assembled relation to Vsaid lever, said ring having diametrically opposite integral lateral extensions adapted for pivotal engagement with a suitable support, the arms of said U-shaped member being of downwardly pointed triangular contour, one side edge of each arm being adapted for joint engagement with a spring biased -element of an electro-thermally responsive overload device, and bothside edges of the respective arms being adapted to jointly engage cooperating shoulders formed upon a suitable support to 'positively limit the pivotal movement of saidv lever in each direction.

15. In an overload circuit breaker, in combination, va molded insulating base having a recess formed therein and opening to the upper and lower ends thereof, a switch mechanism positioned within the upper end portion of said recess v tion corresponding to engagement of said contactor with said contact, said bimetallic member' said lever providing for such tilting of said contactor at will, a molded insulating member slidably mounted within the lower end portion of said recess, a coiled compression spring interposed between said member vand a sidewall of said "recess to bias said member toward a given extreme position, a lug carried by said lever and ,engageable by said member for normal `movement by the latter to a position wherein said contactor is disengaged, a latchv element associated with said member'and projecting downwardly therefrom," a second molded insulating base underlying said base rst mentioned and having a recess opening to the upper end thereof, a bimetallic electro-thermally responsive member -positioned within saiddast mentioned recess and.` having means for connecting the same in circuit with said contact and said contactor upon engagement thereof, a latch element carried by said bimetallic member and adapted to normally engage and hold said iirst mentioned latch element and said insulating member upon movement of the latter against its bias by said lever to a position corresponding to engagement of said contactor with said contact, and said bimetallic member being movable automatically under given overload conditions to effect disengagement of said second latch element fromthe ilrst .to permit movement of said insulating member under its bias to effect corresponding movement of said lever, with consequent disengagement of said contactor from said contact.

16. In an overload circuit breaker, in combination, a molded insulating base having a recess formed therein and opening to the upper and lower ends thereof, a switch mechanism positionedV within the upper end portion of said recess and including a manually operable lever pivotally supported with respect thereto and projecting upwardly therebeyond, said switch mechanism comprising a stationarycontact and a contactor tiltable into and out of engagement therewith, said lever providing for such tilting of said contactor at will, a molded insulating member slidably mounted within the lower end portion of said recess, a coiled compression spring interposed between said member and aside wall of said recess to bias said member toward a given extreme position, a lug carried by said lever and engageable by. said member for normal movement by the latter to a position wherein said contactor is disengaged, a latch element associated with said member and projecting downwardly therefrom, a second molded insulating base underlying said base rst mentioned and having a recess opening to theupper end thereof, a bimetallic electro-thermally responsive member positioned within said last mentioned recess and having means for connecting the same in circuit f with said contact and said contactor upon engagement thereof, a latch element'carried-by said bimetallic member and adapted to normally engage and hold said first mentioned latch element and said insulating member upon movement of the latter against its bias by said lever to a posibeing movable automatically under given overload conditions to eifect disengagement of said second latch element from' the rst to. permit movement of -said insulating member under its ping, overload circuit breaker, in combination, a

molded insulating base having a recess formed therein and opening to the upper`\ end thereof and-a relatively longer recess formed therein and openingto thelower end thereof with a communicating passage formed therebetween, a4

.switch mechanism positioned within said upper recess and including a manually operable lever pivotally supported with respect thereto and pro- .lecting upwardly therefrom, said switch mechanism comprising a stationary contact and a pivoted contactor movable into and out of engagement therewith, said lever having -a spring-biased plunger carried thereby to eect such movements of said` contactor at will upon corresponding movements of said lever, a molded insulating member slidable Within said lower recess, a coiled compression spring interposed between said member and a sidewall of said recess to bias said member toward a 'given extreme position, said memberv having a recess formed therein and opening to the lower surface thereof, a metal member positioned upon the lower surface of said insulating member and interlocked against lateral movement relatively thereto, a coiled compression spring within said last mentioned recess to afford a downward bias upon said metal member, a lug formed integrally with said metal membimetallic member and adapted to normally ena gage and hold saidrst mentioned latch element and said insulating member upon movement of the latter against its bias by said lever to a position corresponding to engagement of said contactor with said contact, said l'iimetallic,memberbeing bendable automatically under given overload conditions to eiect disengagement of said second latch element from the rst to permit movement-oi said insulating member under its bias to effect corresponding movement oi' said lever, with consequent disengagement of said contactor from said contact, and common means for rigidly and permanently connecting said insulating bases and said plate in assembled relationship to each other.

18. In a manually controllable, non-free-trlpping, overload circuit breaker, in combination, a molded insulating base having a recess formed therein and opening to the `upper end thereof and a relatively longer recess formed therein and opening to thelower end thereof with a communicating passage formed therebetween, a switch mechanism postioned'within-said upper recess and including a manually operable lever pivotally supported with respect thereto and projecting upwardly therefrom, said switch mechanism comprising a stationary contact and a pivoted contactor movable into and out of engagement therewith, said ,lever having a spring-biased plunger carried thereby to effect such movements of said contactor at will upon corresponding movements of said lever, a molded insulating memberslidable within said lower recess, a coiled compression spring interposed between said member and a side wall of said recess to bias said member toward a given extreme position,A said member having a recess formed therein and opening to the lower surface thereof, a-metal member positioned upon the ylower surface of said insulating member and interlocked against lateral movement relatively thereto, a coiled compression spring within said last mentioned recess to aiord a downward bias upon said metal member, a lug formed integrally with said metal member and projecting downwardly therefrom, a thin,

`flat insulating plateunderlying said base, said plate having a relatively long slot formed therein to provide clearance for said lug, a second molded insulating base Yunderlying said plate and having a recess opening to its upper end, a bimetallic insulating member havingv shoulders and said lever lugs being engageable with said shoulders to effect movement of said insulating member toward its opposite extreme position against said bias, as`an incident to manual movement of said lever in one direction, said insulating member having a latching lug projecting downwardly l ther efrom, a second molded insulating base having a recess opening to the upper surface thereof, an electro-thermally responsive overload member positioned within said last mentioned recess and having a latching lug normally engaged with said first mentioned latching lug in the last mentioned position of said insulating member, said switch when closed affording a circuit through said overload member, and the latter when subjected to a predetermined overload being adapted to release said insulating member to thereby effect automatic opening ofthe switch.

20. In a manually operable, non-free-tripping, overload circuit breaker for aircraft service, in combination, an upper molded insulating base having recesses opening respectively to the upl per and lower surfaces thereof with an opening electro-thermally responsive member positioned within said last mentioned recess and having means for connecting the same in circuit with said contact and said contacter upon engagement thereof, a latch element carried by said bimetallic member and adapted to normally engage and hold said rst mentioned latch element and said insulating member upon movement of the latter against its bias by said lever to a position corresponding to engagement of said contactor with said contact, said bimetallic member being bend- 4able automatically under given overload conditions to effect disengagement of said second latch element from the rst to permit movement of said insulating member under its bias to eiect corresponding movement of said lever, with consequent disengagement of said contacter from said contact, common means for rigidly and permanently connecting said insulating bases and said plate in assembled relationship to each other, a. pair of wiring terminals positioned at the lower surface of said second base within the contour of the latter, one of said terminalsbeing directly connected electrically with a part of said switch mechanism, and means including said bimetallio element providing an electrical connection between the other terminal and another part of sulating memb'er slidable within the second mentioned recess. a coiled spring associated with said insulating member to normally bias the latter toward one extreme position in the recess, said therebetween, a switch mechanism positioned within the first mentioned recess, said mechanism including a manually operable lever projecting above said base, said lever having a pair of spaced parallel lugs extending downwardly therefrom through said opening, a molded insulating member slidable within the second mentioned recess, a coiled spring associated with said insulating member to normally bias the latter toward one extreme position in the recess, said insulating member having shoulders and said lever lugs being engageable with said shoulders to effect movement of said insulating member toward its opposite extreme position against said bias, as an incident to manual movement of said lever in one direction, said insulating member having a latching lug projecting downwardly therefrom, a second molded insulating base having a recess opening to the upper surface thereof, an electro-thermally responsive overload member positioned within said last mentioned recess and having a latching lug normally overlappingly engaged with said first mentioned latching lug in the last mentioned position of said insulating member, said switch when closed affording a circuit through said overload member, the latter when subjected to a predetermined overload being adapted to release said insulatinf,r member to thereby eiect automatic opening of the switch, and said switch being manually operable to open or closed position by said lever independently of said overload member after initial resetting of said insulating member.

21. In a manually operable, non-free-tripping, overload circuit breaker for aircraft service, in combination, an upper molded insulating base having recesses opening respectively to the upper and lower surfaces thereof with an opening therebetween, a switch mechanism positioned within the first mentioned recess, said mechanism including a manually operable lever projecting above said base, said lever having a pair of spaced parallel lugs extending downwardly therefrom through said opening, a molded insulating member slidable within the second mentioned recess. a coiled spring associated with said insulating member to normally bias the latter toward one extreme position in the recess, said insulating member having shoulders and said lever lugs being engageable with said shoulders to eifect movement of said insulating member toward its .opposite extreme position vagainst said bias, as an incident to manual movement of said lever in one direction, said insulating member having a latching lug projecting downwardly therefrom, a second'molded insulating base having a' recess opening to the upper surface thereof, an electrothermally Aresponsive overload member positioned within said-last mentioned recess and havinga latching lug normally overlappingly vengaged with said first mentioned latching lug in the last mentioned position df said insulating -memben said switch when closed affording a circuit through said overload member, the latter when subjected to a predetermined overload being adapted to release said insulating member to thereby eil'ect automatic opening of the switch, and manually adjustable means associated with said second base and said overload member to vary the degree of overlapping engagement of said latching lugs with each other, whereby the time period of response of the device to a' given overload condition is predetermined.

22. In a manually operable. non-free-tripping, overload circuit breaker for aircraft service, in combinatioman upper molded insulating base having recesses openingr respectively to the upper and lower surfaces thereof with an opening therebetween, a switch mechanism positioned within the ilrst mentioned recess, said mechanism includingv a manually operable lever projecting above said base, said lever having a pair of spaced parallel lugs extending downwardly therefrom through said opening, a molded insulatingr member slidable within the second mentioned recess, a coiled spring associated with said insulating member to normally bias the latter toward one extreme position in the recess. said insulating .'member having shoulders and said lever lugs being engageable with said shoulders to effect movement of said insulating member toward its opposite extreme position against said bias, as an incident to manual movement of said lever in one \direction,`said insulating member having a latching lug projecting downwardly therefrom, a secondmolded insulating base having a recess opening to the upper surface thereof, an electro-thermally responsive overload member positioned within said last mentioned recess and having a latching lug normally overlappingly engaged with said rst mentioned latching lug in the last mentioned position of said insulating member, said switch when closed aiording a circuit through said overload member, the 'latter when subjected to a predetermined overload being adapted to release said insulating member to thereby eiect automatic opening of the switch, manually adjustable means associated with said second base and said overload member to vary the degree-of overlapping engagement of said latching lugs with each other, whereby the time period of re- 23. In a manually operable', non-free-tripping.

- overload circuitA breaker for aircraft service, in

combination, an upper molded insulating base having recesses opening respectively to theupper a coiled spring associated with said insulating member to normally bias the latter toward one extreme position in the recess, said insulating member having shoulders and said lever lugs being engageable with said shoulders to effect movement of said insulating member toward its opposite extreme position against said bias, as an in- Ncident to manual movement of said' lever in one i direction, said insulating member having a latching lug projecting downwardly therefrom, a second molded insulating base having a recess opening to the` upper surface thereof, an electro-thermally responsive overload member positioned within said last mentioned recess and having a latching lug normally engaged with said first mentioned latching lug in the last mentioned position of said insulating member, said switch when closed affording a circuit through said overload member, the latter when subjected to a predetermined overload being adapted to release said insulating member to thereby eiect automatic opening of the switch, said switch being manually operable to open or closed position by said lever independently of said overload member after initial resetting of said insulating member, and said switch mechanism being adapted for retention thereof in closed position by continued manual engagement of said lever regardless of the condition of said overload member.

Y 24. In a manually operable, non-free-tripping, .overload circuit breaker for aircraft service. in combination, an upper molded insulating base having recesses opening respectively to the upper and lower surfaces thereof with an opening therebetween, a switch mechanism positioned within the first mentioned recess, said mechanism including a manually operable lever projecting above said base, said lever having a pair of spaced parallel lugs extending downwardly therefrom through said opening, a molded insulating member slidable within the second mentioned recess, a coiled spring associated with said insulating member to normally bias the latter toward one extreme position in the recess, said insulating member having shoulders and said lever lugs being engageable with said shoulders to eilect movement of said insulating member toward its opposite extreme position against said bias, as an incident to manual movement of said lever in one direction, said insulating member having a latching lug'proiecting downwardly therefrom, a.

independently of said overload member after and lower surfaces thereof with. an opening therebetween, a switch mechanism positioned Within the rst mentioned recess, said mechanism including a manually operable lever projecting above initial resetting of said insulating member, said switch mechanism being adapted for retention thereof in closed position by continued manual engagement of said lever regardless of the condition of said overload member, a pair of wiring terminals accessible at the lower surface of said second base, one of said terminals being electrically connected with a part of said switch mechanism, and the other terminal being electrically connected with said overload member.

25. In a manually operable, non-free-tripping, overload circuit breaker for aircraft aservice, in combination, an upper molded insulating base having recesses opening respectively to the upper and lower -surfaces thereof with an opening therebetween, a 4switch mechanism positioned within the iirst mentioned recess, said mechanism including a manually operable lever projecting above said base, said lever'having a pair of spaced parallel lugs extending downwardly therefrom through said opening, a molded insulating member slidable Within the second mentioned recess, a coiled spring associated with said insulating member to normally bias the latter toward one extreme position in the recess, said insulating member having shoulders and said lever lugs being engageable with said shoulders to effect movement of said insulating member toward its opposite extreme position against said bias, as an incident to manual movement of said lever in one direction, said insulating member having a latching lug projecting downwardly therefrom, a second molded insulating base having a recess opening to the upper surface thereof, an electro-thermally responsive overload member positioned within said last mentionedrecess and having a latching lug normallyv engaged with said.

iirst mentioned latching lug in the last mentioned position of said insulating member, said switch when closed aording a circuit through lsaid overload member, the latter when subjected to a predetermined overload being adapted to release said insulating member to thereby eiect automatic opening of the switch, said switch being manually operable to open or closed position by said lever independently of .said overload member after initial resetting of said insulating member, said switch mechanism being adapted for retention thereof in closed position by continued manual engagement of said lever regardless of the condition of said overload member, a pair of wiring terminals accessible at the lower surface of said second base, one of said terminals being electrically connected with a part of said switch mechanism, the other terminal being electrically connected with said overload member, and said overload member being electrically connected with another part of said switch mechanism.

26. In an electro-thermally responsive overload circuit breaker, in combination, a normally fiat bimetallic strip of predetermined caliber, means for connecting said strip in an electric circuit to provide for response thereof to a given overload condition in the circuit, a switch for controlling said circuit, said switch being manually operable to open or closed position onder all conditions, spring means for biasing said switch toward open position, a latch member attached to said strip and normally engaging a part of said switch when closed to restrain the action of said biasing spring, means for supporting said strip at each end, and the supporting means for one end of said strip being manually adjustable to move said end of the strip to vary the normal plane of the latter, whereby the initial position of said latch member is correspondingly varied to thereby predetermine the period of latch-tripping response vof said bimetallio strip to a given overload condition, the supporting means for the other end of said strip permitting the aforementioned adjustment of the plane thereof without bending.

27. In an electro-thermally responsive overload circuit breaker, in combination, a manually operable switch mechanism all parts of which are normally biased to circuit interrupting position, a

normally iiat bimetallic strip of predetermined caliber included in the circuit controlled by said switch, a latch member carried by said strip and cooperating with said switch to normally hold the latter, when closed, in circuit completing position against said bias, normally fixed means at each end of said strip for supporting the same in a predetermined plane, manual adjusting means at one end of the strip, said means when manually adjusted being adapted to vary the initial plane of said strip and the corresponding initial position of said latch, to thereby vary the time element of response of said bimetallic strip for tripping of said switch under a given overload condition, and said switch being adapted for manual retention in circuit completing position independently of said latch.-

28. In an electro-thermally responsive overload circuit breaker, in combination, a switch biased to open position and adapted for manual movement to and retention in closed position at will, a normally iiat bimetallic strip of predetermined caliber, means for connecting said strip in the circuit controlled by said switch to normally provide for response of the former to a given n overload condition in said circuit, a latch member attached to said strip and projecting therefrom, normally fixed means at each end -of said strip for supporting the same, the supporting means for one end of said strip being manually adjustable to move said end of the strip to vary the normal plane of the latter, whereby the initial position of said latch member is correspondingly varied to thereby predetermine the period of latch-tripping response of said bimetallic strip to a given overload condition, and means comprising a heating element associated with said bimetallic 'strip and also included in said circuit, said heating element acting under given overload conditions to modify the operating characteristics of said bimetallic strip under overload conditions.

ALVIN W. KRIEGER. 

